How to make particles appear where I draw weight using dynamic paint?
There is an interesting workaround, found by Blenderartists member suboptimal - http://blenderartists.org/forum/show...inally-working


First you need to uv unwrap your Canvas and add two dynamic paint
canvassesses (Whats the plural?)
The first one is gonna generate the Time Map, the other one the
Density Map. Make sure you turn of dry and slow because otherwise the
particles later will behave a bit weird.
The dissolve time for the Time map canvas must be as long as the
particles are going to be emitted.





Then setup your brush with a white color. You have to use Mesh Volume
or Particle system with 0 smooth raduis as the paint source (nothing
with a blurred edge)





Then bake your dyn paint image sequences, the frame range must be the
same as your particle emission frame range.
Take the last frame of each one of your sequences and fill its
transparent background with black.
Add a particle system, it should have a pretty big amount of
particles. Next step is using them as particle textures, go to the
texture tab select particle textures ( I think they aren't in cycles
yet, only in BI). Load the Time Map, mapping to uv etc. and check
Time in the influence tab.
Repeat it for the density Map but use Density influence this time.